J.R. Jennings was a Starfleet officer in the 23rd century.

In 2285, he was an admiral at Starfleet Academy's Starfleet Training Command. He was the Director of Educational Services - Starfleet Training Command. His office, located on the second level of a building, was in room #202. His rank, name, position, and office were listed on a directory placard. (Star Trek II: The Wrath of Khan, set artwork)

This character was only mentioned in writing.
He was named after art director and production designer Joseph R. Jennings. The placard was sold on It's A Wrap! sale and auction for US$31.99. [1]